what is 3:2 pulldown?

[Endrat]

hi..

what is 3:2 pulldown? any example ?
help me to understand it...thanks!

[amilkis]

TV in the US (NTSC) Runs at 30 frames per second. Film runs at 24 fps. A method was needed to convert 24fps film to 30fps TV and still maintain lip sync. The method that was created is called 3:2 pulldown (it has many names, including 2:3 pulldown, cine expansion, film expansion, etc.)
Every frame of TV is made up of two fields, odd number lines and even number lines. The additional 6 frames needed are created by combining fields from different frames to create in-between, or "jitter" frames.
It works like this:

WHOLE FRAME - WHOLE FRAME - WHOLE FRAME - JITTER FRAME - JITTER FRAME

What you are left with is a pattern... 3 whole frames, 2 jitter frames, 3 whole frames, 2 jitter frames, 3 whole frames, 2 jitter frames, etc. Hence the name, 3:2 pulldown.

When compositing, you generally need to remove the jitter frames, do your compositing, and then re-insert the jitter frames when rendering (or after your render). In Combustion, click on the icon for the footage of a layer (or in the footage library). Click on Source, and in the source window you will see a button called "Guess 3:2 Sequence." If you click that button, Combustion will analyze the footage, find the 3:2 pattern, and remove it. Once identified, the pop up menu above teh "Guess 3:2" button will show you the pattern. Using the pattern listed above, the pop up would show a pattern of "WWWSS" for 3 whole frames and 2 jitter frames. When you go to render your comp, you need to enter in the same pattern in the render settings box to put the 3:2 pulldown back in.

For a more in depth and generic (non combustion specific) description of 3:2 pulldown, check out the following FXGuide Tip:

http://www.fxguide.com/fxtips-54.html

Hope this helps!

-Andy

[Endrat]

hi Andy!

thanks for your refs...